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Springtime in Vegas

Spring is upon us! Glorious Spring when the world is bursting with new life and thoughts turn to... the IMPACT conference. Yes, that's right, I said the IMPACT conference. Forget all that stuff about bunnies, baby birds and blooming backyard blossoms and get yourself to Vegas, baby!

Here's the deal - I've been attending these things since the CICS conference was expanded to include WebSphere MQ and it became the first "Transaction & Messaging Conference." Back then the dates moved around a bit and at one point we were in Vegas in June. Fortunately, cooler heads prevailed (and if you've ever been in Vegas in June you know I mean that literally as well as figuratively) and the dates seem to have settled down to the April/May time frame. Aside from that being a great time of year weather-wise, it also happens to follow closely on the heels of IBM's Spring announcement cycle so IMPACT is always your first chance to get in-depth info on whatever is new that year. If you've been following the WebSphere family for a while you know there's a lot of R&D investment in the brand as well as some excitingacquisitions so there's ALWAYS something cool to talk about at the conference.

I also am excited to get a chance to talk to you and evangelize a bit about security. In addition to my usual security sessions this year I'll be co-presenting with AJ Aronoff from Prolifics. AJ and I first co-presented a few years back after meeting on a customer engagement and he's been focused on security ever since. Over the last couple of years he's extended that security focus to include automation, instrumentation, monitoring and recovery. These are things I've been recommending but have not been on an engagement long enough to actually help build them so I'm excited to see what AJ's been doing in that regard. I always learn something from AJ and he's quite a character so I'm looking forward to this presentation. I'm sure you will find it helpful and fun as well so I hope you will attend.

Another reason I'm excited about this year's IMPACT is that I lobbied to get more advanced content included in the agenda and my favorite session of all time has returned! If you use WebSphere MQ at all as an administrator, developer, operator or architect you absolutely MUST get to the WebSphere MQ Internals session. Since the internals are not documented publicly, this is information that will NEVER end up in the Infocenter and NEVER make it into the formal education. The only way to get it is either to the conference or to set up recording devices in the The Dolphin Inn adjacent to the Hursley House grounds. Of the two, hanging out in The Dolphin has it's charms but attending the conference is by far the more efficient way to gather such info.

I'll give you an example of how cool the Internals sessions are. Many years ago in one such session Mark Taylor explained that queue handles are managed internally on a stack. One effect of this is that WMQ is more performant than if, for example, these were managed in a pipe or a queue. A side effect is that if message rates are slow enough, only one application instance will ever get a message. Consider the following sequence of events:

Five application instances start and listen on the same queue

A message arrives and is handed to App01

App01 processes the message and issues a new GET on the queue

WMQ pushes the handle for App01 onto the stack

A new message arrives and is handed to the handle on the top of the stack - that of App01

The behavior with a low volume flow is that App01 will handle all the messages. As the message volume increases, new messages arrive before App01 has completed and so now App02 begins to see some activity. As the message rate continues to rise, App04 and eventually App05 begin to see some action. Eventually as message rates decline, the apps with handles at the bottom of the stack go idle, even though other instances appear to be running full speed.

If you haven't been to the WebSphere MQ Internals session at the conference, this behavior might seem counter-intuitive. In fact, I've seen many PMRs opened with subject lines like "WebSphere MQ not distributing workload" that turned out to be "working as designed" because the message flow volume was so low that only one or two application instances were ever handed a message.

That's an example of just one way that understanding the internals of the QMgr helps you to tune it and design appropriate architectures. It's been a while since this session was offered and I'm dying to see what's new. I just hope it isn't scheduled opposite my sessions! I'd hate to miss it and I'd hate for attendees to be forced to choose between that and a security session.

Of course, there's a lot more about this year's IMPACT that I'm really excited about and I hope to see you there. Since I had a hand in the planning this year if there's anything you especially like (or dislike) be sure to let me know. See me in the hall after the MQ Security session.